How to create an array under an alreay present key in PHP? -

i've following array titled $grid_data follows:

    array (     [0] => array         (             [question_id] => 50147             [question_parent_id] => 0             [question_subject_id] => 4             [question_topic_id] => 219             [question_directions] =>              [question_text] => wooden scale of length l , mass m lying on frictionless table. particle of mass m moving velocity v, @ distanced centre shown in fig. 93 strikes scale , adherses it. of follwoing quantity (quantities) (are) conserved system.               [question_solution] =>              [question_file] =>              [question_description] =>              [question_difficulty_type] => 2             [question_has_sub_ques] => 0             [question_picked_individually] => no             [question_appeared_count] => 0             [question_manual] => 0             [question_has_solution] => 0             [question_site_id] =>              [question_created_staff_id] => 4e4078987c90dbf4ee477f480ad1b874             [question_added_date] => 1329728799             [question_updated_staff_id] => 1096ab29ecde5cec198bb2ebe730d229             [question_updated_date] => 1340253386             [que_issue_id] => 1             [reported_site_id] => entprm             [reported_user_type] => student             [reported_user_id] => 395599c5891c1418357e2efa89bc3e27             [que_issue] => question wrong,other             [que_issue_comment] => happy question             [que_issue_status] => 0             [que_issue_date] => 1394517725             [que_issue_fixed_date] => 0             [question_lock] => 1             [ques_ans] => array                 (                     [0] => array                         (                             [answer_id] => 198739                             [answer_question_id] => 50147                             [answer_text] => linear momentum                             [answer_file] =>                              [answer_description] =>                              [answer_is_right] => 0                         )                      [1] => array                         (                             [answer_id] => 198740                             [answer_question_id] => 50147                             [answer_text] => angular momentum                             [answer_file] =>                              [answer_description] =>                              [answer_is_right] => 0                         )                      [2] => array                         (                             [answer_id] => 198741                             [answer_question_id] => 50147                             [answer_text] => kinetic energy                             [answer_file] =>                              [answer_description] =>                              [answer_is_right] => 0                         )                      [3] => array                         (                             [answer_id] => 198742                             [answer_question_id] => 50147                             [answer_text] => linear momentum , angular momentum both                             [answer_file] =>                              [answer_description] =>                              [answer_is_right] => 1                         )                  )          )      [1] => array         (             [question_id] => 21679             [question_parent_id] => 0             [question_subject_id] => 5             [question_topic_id] => 285             [question_directions] =>              [question_text] => in electrical cable there single wire of radius 9 mm of copper. resistance �math xmlns=�http://www.w3.org/1998/math/mathml���mn�5�/mn��mo��nbsp;�/mo��mi��#937;�/mi��/math�. cable replaced 6 different insulated copper wires, radius of each wire 3mm. total resistance of cable             [question_solution] =>              [question_file] =>              [question_description] =>              [question_difficulty_type] => 2             [question_has_sub_ques] => 0             [question_picked_individually] => no             [question_appeared_count] => 0             [question_manual] => 0             [question_has_solution] => 0             [question_site_id] =>              [question_created_staff_id] => fbfee12504bf3c4a038d4c9f142f894e             [question_added_date] => 1326440661             [question_updated_staff_id] => 1096ab29ecde5cec198bb2ebe730d229             [question_updated_date] => 1338368619             [que_issue_id] => 2             [reported_site_id] => entprm             [reported_user_type] => staff             [reported_user_id] => ff8d4a5ea6bf11dce105aa2fa7b959b8             [que_issue] => question incomplete/wrong,directions missing             [que_issue_comment] =>              [que_issue_status] => 0             [que_issue_date] => 1395655234             [que_issue_fixed_date] => 0             [question_lock] => 1             [ques_ans] => array                 (                     [0] => array                         (                             [answer_id] => 573122                             [answer_question_id] => 21679                             [answer_text] => «math xmlns=¨http://www.w3.org/1998/math/mathml¨»«mn»7«/mn»«mo».«/mo»«mn»5«/mn»«mo»§nbsp;«/mo»«mi»§#937;«/mi»«/math»                             [answer_file] =>                              [answer_description] =>                              [answer_is_right] => 1                         )                      [1] => array                         (                             [answer_id] => 573123                             [answer_question_id] => 21679                             [answer_text] => «math xmlns=¨http://www.w3.org/1998/math/mathml¨»«mn»45«/mn»«mo»§nbsp;«/mo»«mi»§#937;«/mi»«/math»                             [answer_file] =>                              [answer_description] =>                              [answer_is_right] => 0                         )                      [2] => array                         (                             [answer_id] => 573124                             [answer_question_id] => 21679                             [answer_text] => «math xmlns=¨http://www.w3.org/1998/math/mathml¨»«mn»90«/mn»«mo»§nbsp;«/mo»«mi»§#937;«/mi»«/math»                             [answer_file] =>                              [answer_description] =>                              [answer_is_right] => 0                         )                      [3] => array                         (                             [answer_id] => 573125                             [answer_question_id] => 21679                             [answer_text] => «math xmlns=¨http://www.w3.org/1998/math/mathml¨»«mn»270«/mn»«mo»§nbsp;«/mo»«mi»§#937;«/mi»«/math»                             [answer_file] =>                              [answer_description] =>                              [answer_is_right] => 0                         )                  )          ) ) 

now ignore rest of array , concentrate on 2 key elements above array follows:

[que_issue] => question wrong,other //from first array [que_issue] => question incomplete/wrong,directions missing //from second array 

actually want convert comma separated strin array under key [que_issue] every array element present in array. want output in following manner in above array($grid_data):

/*oputput first array element array `$grid_data`*/  [que_issue] => array( [0] => question wrong [1] =>other ) /*oputput second array element array `$grid_data`*/ [que_issue] => array(     [0] =>  question incomplete/wrong     [1] =>  directions missing     ) 

now can me in manipulating array $grid_data in order have above output each array element present in it? in advance.

easy enough foreach , explode:

foreach($grid_data &$array) {     $array['que_issue'] = explode(',', $array['que_issue']); } 

or:

foreach($grid_data $key => $array) {     $grid_data[$key]['que_issue'] = explode(',', $array['que_issue']); }